Absorbent articles, such as diapers and adult incontinence products, are well known articles of commerce. Multiple attempts have been made to provide them with an overall good fit and with a high absorbent capacity. Modern diapers make use of absorbent polymer materials also known as superabsorbent polymers, which allow for storage of significant amounts of aqueous liquids (e.g., on the order 300 ml for a typical baby diaper).
While such an absorbent article is generally a disposable product, it is frequently worn over many hours and worn in a dry state as well as in a urine loaded state. As a result, providing good wearing comfort is very important both when the article is dry and when the article is fully or partially loaded with urine (or other bodily liquids).
One way the art has approached wearing comfort is to provide thinner diapers. For example, U.S. Pat. No. 4,673,402 describes an absorbent article with a dual layer core where the lower core component has a relatively high concentration of superabsorbent material and a relatively high density. U.S. Pat. No. 5,102,597 describes absorbent polymeric macrostructures that comprise an interparticle crosslinked aggregate where individual superabsorbent particles are reacted with an interparticle crosslinking agent to form an aggregate which may take a sheet form. U.S. Pat. No. 5,411,497 discloses an absorbent article which includes superabsorbent material located in discrete pockets formed between a first and a second carrier layer and water-sensitive attaching means for securing the carrier layers together to form the pockets. U.S. patent application Ser. No. 10/776,839 discusses absorbent articles with a discontinuous layer of absorbent polymer material. The layer may contain up to 20% of an absorbent fibrous material.
The art has also considered improvement to the absorbent polymer materials that are a component of modern diaper cores by improving the capacity and/or permeability thereof. The hydrogel forming absorbent polymer disclosed in U.S. Pat. No. 5,599,335 has a Performance Under Pressure capacity of at least about 23 g/g and a Saline Flow Conductivity of at least about 30×10−7 (cm3 seconds)/g. U.S. Pat. No. 6,710,225 describes superabsorbent materials with a Modified Absorbency Under Load value of not less than about 20 g/g and a Tau value (time to reach 60% of equilibrium absorption capacity) of not less than 0.8 min.
Absorbent structures comprising differing superabsorbent materials are also discussed. European Pat. No. 401 189 B2 discusses absorbent articles with two separate layers made up of different superabsorbents; one of the superabsorbents has a high absorption rate, the other superabsorbent has a high liquid retention rate under pressure. The superabsorbent layers are separated by one or more distance maintaining layers. U.S. Pat. No. 5,728,082 describes a first fluff layer with a first superabsorbent material mixed thereinto, the first superabsorbent having a high degree of crosslinking, and a second layer which contains a second superabsorbent having a higher liquid absorbency than the first superabsorbent. U.S. Pat. No. 5,836,929 discusses absorbent articles with an upper layer that consists mainly of a first superabsorbent material with a Gel Layer Permeability value of at least about 4×10−7 (cm3 seconds)/g and a lower assembly with an Absorption Against Pressure of at least 15 g/g. The upper layer also has void space for storage and redistribution of liquid discharges.
The art also has recognized the need for softening structures comprising high levels of absorbent polymer material. For example, U.S. Pat. No. 5,868,724 teaches slitting structures such as those described in the aforementioned U.S. Pat. No. 5,102,597. However, a treatment of this type may result in breaking interparticulate crosslinks reducing the stability of the structure.
However, there is a continuing need for absorbent articles having improved thinness and softness that maintain the capability to acquire and store enough of the fluid deposited thereon so as to continue to provide desirable wearer skin dryness and satisfactory leakage performance. Caregivers and adult wearers of such absorbent articles desire improved discretion in order that a diaper is less visible under clothes or, in the case of an infant diaper, looks more like underwear. More conformable cores are desired in order to reduce the amount of material placed between a wearer's legs.